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    Home > Biochemistry News > Biotechnology News > Professor Dong Guangbin leverages Catellani reaction to synthesize whole carbon tetratose instead of olefins

    Professor Dong Guangbin leverages Catellani reaction to synthesize whole carbon tetratose instead of olefins

    • Last Update: 2020-05-31
    • Source: Internet
    • Author: User
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    The natural product molecules containing all-carbon tetra-four seinos (Photo: Resources 1)Since these olefins can glow and heat in many fields of study, people have also tried to find simple and efficient means to construct the structureHowever, the modification of the four alpha-carbon groups on both sides of the olefin C-C double-bond can lead to a more crowded spatial structure, many bit-impeded reaction reagents close to the reaction site is very difficult;so far, the carbon metallization of hydrocarbons is the most effective strategyThis method is based on internal hydrocarbons and reacts in three components with other organic metal reagents, halogenated hydrocarbons or organic boric acidTwo of the olefins' replacement bases come from the internal hydrocarbons, while the other two substitute bases come from the other two reactionsDifferent substrates are widely sourced and diverse, so the replacement base of the appropriate modification of substrate modification can be obtained from a variety of structures of four replacement all-carbon olefins, flexible and convenientHowever, in order to ensure that the other two reactants can be regionalselective and hydrocarbon substrate coupling, to obtain a single structure of the product, it is necessary to internal hydrocarbon seamount space level resistance or electronic characteristics of a certain difference, otherwise it is easy to form a regional isomerIn addition, the limited variety of cyclocarbons means that the carbon metallization process has a greater advantage in the synthesis of non-ring-shaped olefins, but the construction of ring-shaped olefins is more chicken ribsthe synthesis of refined hydrocarbons to replace olefins (Photo: Source: Supplied)Recently, Professor Dong Guangbin of the University of Chicago in the United States has taken a different approach, using the Catellani reaction of chlor-olefins to enable the efficient construction of a series of ring-shaped and non-ring-shaped whole carbon tetracarbons to replace olefinsThe reaction has good regional selectivity and substrate applicability, the results of the study are published in Nature's sub-journal Nature Chemistryimage source: Reference s1
    In 1997, a team of Professor Marta Catellani of the University of Parma, Italy, found that a collaborative catalytic system of Pd catalysts and ice-lowering tabletenes (NBE) could be used to synthesize multi-replaceal aromatic sofones simply and efficientlyThe reaction starts from the iodine-based aromatic hydrocarbon, oxidizes the Pd catalyst and forms the aromatic niobium intermediate, the species further inserts the C-C double bond of NBE, and the adjacent C-H bond is activated with the aid of the alkali, and obtains the aromatic-based ice-lowering crucifile hemerus(ANP), ANP further With iodized alkanes oxidation addition and reduction elimination will be introduced in the adjacent location of iodized aromatic hydrocarbons alkyl substitution base, so that the same replacement base can also be introduced in another neighbor, followed by beta-C elimination of the aromatic niobium intermediates that are replaced with the base modification, the species further with the olefin Heck reaction will be the final productThe whole process is equivalent to the introduction of pro-electric reagents in the adjacent location of iodine-based aromatic hydrocarbons, and the introduction of pro-nuclear reagents in this place, thus achieving the construction of multiple replacement aromatic hydrocarbonsThe catalytic cycle of the Catellani reaction (Photo: Source: Supplied) a series of series of series of series of series of soeries called the Catellani reaction, the application of the substrate has been further expanded, and other halogenaromatic hydrocarbons (e.g brominated aromatic hydrocarbons) can also be involved in the reaction The adjacent location of halogenaromatic hydrocarbons also modifies aromatic groups, and can be used to control the sequence of materials added by different substitution base modifications, the resulting replacement of aromatic niobium intermediates in addition to C-C key cross-coupling, but also can participate in C-N, C-O key formation and other processes Inspired by this, Professor Dong Guangbin's team envisions the construction of a full-carbon four-replaces olefin by the dual-functionalization of halogenic olefin-based C-H and C-X bonds under the role of the same catalytic system, using halogenic olefins as a substrate Each sub-reaction of the tellani reaction can be carried out in sequence, even if the spatial level resistance and electronic characteristics of the two sides of the olefin smaller difference, will not affect the regional selectivity of the reaction, and compared to the ring-like hydrocarbon, the type of cyclo-olefin is more abundant, the application range of the substrate can be greatly broadened However, there is a significant difference between the aromatic structure of aromatic hydrocarbons and the c-C double-bond reaction activity of olefins, which also means that the Catellani reaction in which halogens are involved and cannot be rigidly applied in the past, the difficulty is mainly reflected in the following aspects: (1) the c-C double-bond of olefins is prone to cyclolineization side-effects when participating in the reaction Professor Marta Catellani discovered as early as 1982 that bromine olefins, when mixed with NBE, tend to form two cyclopropropylene products by 3-exo-trig, unable to obtain an ene-based ANP intermediates (2) The above 3-exo-trig route of cyclopropane into a reversible process, the appropriate control of the reaction conditions may restore the state of the ene-based ice-lowering tablet-based crucifiel intermediate, but if the base of the acrylic propylene bit is beta-H, then further beta-H elimination, which leads to irreversible formation of cyclopropane products (3) In the past, when halogenaromatic aromatic hydrocarbons react with NBE, two C-H bonding canopy occurs with the help of the substrate in both adjacent positions of halogen aromatic hydrocarbons are introduced to replace the base, through the spatial bit resistance effect to promote the aromatic-lowered ice-falling substrate base crucible species anti-insertion (beta-C elimination) If the alpha bit of halogenated olefins does not have a spatial-oriented substitution base, the corresponding ole-based ice-lowering tablet-based radon species may be difficult to reverse-insert difficulties in the participation of halogenic olefins in the Catellani reaction (Photo: Source: 1) Professor Dong Guangbin's team carefully analyzed the catalytic cycle process of halogenic olefins participating in the Catellani reaction, and he believes that two of these primitive processes may lead to cyclopropylene, the olel-based pyreobium species inserted after NBE, if the oleic C-H key radon is further inserted into the intermediate i of the informing of ene-based ananptonic In addition, after the reaction of pro-electric reagents with ene-based ANP, the cyclopropane process can occur again if the rate of reverse insertion occurs in intermediate III is slow From this point of view, the key to the success of the response is to minimize the propane of the 3-exo-trig pathway and to accelerate the C-H coking and anti-insertion (beta-C elimination) process halogen-based olefins participated in the reaction process of the Catellani reaction (Photo Source: Resources 1) the authors began to explore the reaction conditions, the use of the NBE reaction that replaced the base modification may hinder the propane (insertion) of the cyclopropane (insertion) due to its increased spatial bit resistance, and promote the beta-C elimination (anti-insertion) process They took bromine-based olefin 1a as the template substrate, iodine positive butane 2a as a pro-electric reagent, acrylate 3a, examined a series of different replacement base modification nBE participation in the reaction, found that the choice of C2-bit modified N-methylamide group NBE can obtain the best reaction effect, olefin dual-organic target product yield is the highest, the secondary reaction pathway is greatly inhibited No replacement base and NBEene base far-end modification can not be able to obtain the target product, C2-bit replacement base is small or larger is not conducive to the effective reaction the effect of nBE participation in the reaction of different structures (Photo source: reference material s1) they further use trifluoroquineurenie 5a as the template substrate to adjust the Pd catalyst and its ligands, solvents, reaction temperature and other parameters, and finally determine the optimal reaction conditions The optimization of the reaction conditions of (Image Source: Source: Resources 1) the Catellani reaction in which this halogenic olefin is involved has good applicability to most ring/non-ring trifluorophaphaphanateors or bromine-based oleumphonites and olefinpronuclear reagents, and different sensitive military groups can be well compatible with the reaction system For iodized alkanes, the yield of the target product will be reduced to a certain extent when the substrate with large spatial resistance participates in the reaction, and the secondary alkyl iodide is more difficult to approach the ene-based ANP due to the influence of spatial bit resistance, so it is not possible to participate smoothly in the reaction In addition, the catalytic system is suitable not only for C1-bit Heck reactions, but also for Suzuki coupling, hydrogenation, C2-bit aramid, and molecular-in-a-neighbor alkylation/prototype Heck coupling series ringing processes study of the scope of application of the substrate (Photo Source: Source: 1) subsequently, the author explored the dynamics of the reaction using the example of trifluophonice-based ester 5a, which gave a first-level response to Pd/L1, and to 5a, 2a, 3a and N11 are both zero-grade, meaning that 5a to Pd catalyst oxidation and further N11 insertion, ene-based ANP and pro-electric reagent 2a reaction, pro-nuclear reagent 3a insertion process is not the final step of the reaction Reducing the load of N11 can lead to an increase in the by-product of a direct Heck reaction, indicating that the N11 insertion process is a pre-balanced step, which occurs before the final step Thus, only the process of forming anene-based ANP may become a critical step in affecting the reaction rate They further designed the Dynamic Isotope Effect (KIE) experiment, where C-H key breakage is part of the decisive step, and there should be a primitive reaction to determine the rate of reaction before and after that study of the reaction mechanism (Photo: Source: Resources 1) to demonstrate the practical value of this method, they also tried to use the reaction to synthesize the thickened tricyclic compound 14 In the past, a seven-step reaction was required to complete, the author started from trifluoroquineureni6y, only three steps of reaction to complete the efficient construction of 14, the synthesis route has been significantly simplified synthesis of the compound 14 (Photo Source: Resources 1) In short, Professor Dong Guangbin's team, based on previous research work, studied the mechanism of the reaction in depth, overcoming the problem of cyclopropane when halogenated olefins participated in the Catellani reaction, and thus opened up a new way to construct a whole carbon tetra-carbon alternative olefin The resolution of nearly 40 years of outstanding issues has also laid a solid foundation for further expansion of the application of Pd/NBE collaborative catalytic systems in other reactions Reference s Dywedodd y regioselective synthesis of all-carbon tetrasubstituted olefins enabled by an alkenyl Catellani reaction Nat Chem., DOI: 10.1038/s41557-019-0358-y Nickel-Catalyzed Three-Component Domino Reactions of Aryl Grignard Reagents, Alkynes, and Aryl Halides Llys Llywodraeth J Am Chem Soc., DOI: 10.1021/ja513166w A Catalytic Complex Cycle to a Regioselective Synthesis of o, o'ddisubstituted vinylarenes Angew Chem Int Ed., DOI: 10.1002/anie.199701191 Stereocontrolled Synthesis of Tetrasubstituted Olefins Chem Rev., DOI: 10.1021/cr050051k
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